1. Field of the Invention
The field of the invention is directed to devices for purging the pitot tube and outside static lines of an aircraft by the introduction of a gaseous media under pressure.
2. Description of Prior Art
Applicant is aware of the following patents which, in his opinion, are most relevant to the subject invention.
U.S. Pat. No. 3,380,298 to V. W. Hanson discloses a device for purging the pitot tubes of aircraft which utilizes three individually operable solenoid valves 10, 12, and 14 which are controlled by means of a toggle switch 22 which is manually operable between "purge", "vent", and "read" positions as the switch lever is shifted to one or the other of positions "A", "B", or "C". The three solenoid valves, switches, and accessory components are housed within a metal box 25 which is provided with a thermostatic electric heater to maintain a selected temperature and prevent freezing.
A pilot is able to "read" on a manometer 29 the pressure of pitot tube 27; or by moving the toggle of a toggle switch 22 to position B, to "vent" said system; or by moving said toggle to position A, to purge the pitot tube by introducing filtered compressed air from a tank 24 to the pitot tube while closing air intake 31 by means of solenoid valve 10-16. During those periods of time when the pitot tube is being "vented", intake 31 is open to the atmosphere and solenoid valves 10-16, 12-18, and 14-20 are closed for preventing the introduction of compressed air into the system and for effecting a circulation of air from the atmosphere to the pitot tube.
When it is desired to "read" the pressure, solenoid valve 10-16 remains closed to prevent the introduction of compressed air into the system; however, solenoid valves 12-18 and 14-20 are open to apply the "velocity pressure" and static pressure from the pitot tube to manometer 29.
After the manometer has been "read" the toggle switch is returned to position A to resume purging.
U.S. Pat. No. 2,016,926 to J. Josepowitz discloses Apparatus for Emptying and Cleaning Beer and Other Pipes by means of compressed air from tank 12 which is introduced into the pipes to be cleaned when one or more air-control valves are manually opened.
U.S. Pat. No. 3,327,530 to F. P. Lepird discloses a Marine Speedometer which includes a pitot tube (strut) 12 having an opening 20 therein which is connected to an indicator 16 by means of conduits 26 and 28 which are disposed on opposite sides of a manually operable valve 30 which includes a line in which a plunger 58 is reciprocably mounted. A spring 62 normally urges the plunger to the left for locating a passageway 66 in open communication with conduits 26 and 28. The plunger is shifted to the right against the counterforce of spring 62 by air pressure introduced against the left end of the plunger via a source 38 of pressurized fluid, to wit a pump the piston of which is manually reciprocated by means of a stem 98 which terminates in a handle 122. Movement of plunger 58 to the right moves passageway 66 out of relationship with conduits 26 and 28 for placing conduit 26 in open communication with pump 38 whereby air is forced through opening 20 of the pitot tube 12 to purge same. The plunger 58 will automatically shift to the left for restoring communication between conduits 26 and 28 via passageway 66 of the plunger when the pumping action is discontinued.
Applicant is unaware of any prior art more relevant to the subject invention than the disclosures of the references discussed, supra, none of which disclose, suggest, or relate to a spool valve having associated therewith a self-contained source of gaseous media under pressure.